In the course of developing successive generations of cellular telephones a great deal of effort has been spent on reducing the volume of the wireless terminal. Coupled with this reduction in the overall volume has been the desire to reduce the volume of the antenna whilst still maintaining its sensitivity. Externally mounted monopole antennas have been succeeded by internal antennas such as PIFAs (Planar Inverted-F Antennas) and notch antennas.
United States Patent Application Publication US 2003/0103010 A1 discloses a handset having a dual band antenna arrangement including a PIFA. PIFAs are popular with some manufacturers of handsets because they exhibit low SAR (Specific Absorption Rate) performance (and thereby less loss to the head) and they are installed above the phone circuitry and, therefore, “re-use” the space within the phone to some degree. The PIFA disclosed in this cited specification comprises a planar patch conductor mounted adjacent to, but spaced from, a ground conductor, usually a printed circuit board having at least the RF components mounted thereon. A first feed conductor is connected to the patch conductor at a first point, a second feed conductor is connected to the patch conductor at a second point, and a ground conductor is connected to the patch conductor at a third point located between the first and second points. The impedance to which the antenna is matched can be changed by altering the relative thicknesses of the first, second and ground conductors. The PIFA is fed by a diplexer to which for example GSM and DCS circuitry is connected. In a variant the planar patch antenna has a slot which can be considered as dividing the planar conductor into two differently sized antennas connected to a common feed. The smaller of the two antennas is coupled to receive DCS frequencies and the larger of the two antennas is coupled to receive GSM frequencies. However, such antennas are physically large and are difficult to use over more than two cellular bands.
U.S. Pat. No. 6,424,300 B1 discloses notch antennas for use in portable wireless terminals. The notch antenna is preferably formed in the ground plane conductor of a printed circuit board (PCB) that has RF circuitry thereon for receiving and transmitting RF signals. In this specification the notch antenna may be used as a primary antenna for radiating and receiving wireless communication signals or as a secondary antenna for receiving signals such as Bluetooth® or Global Positioning Signals (GPS). When the notch antenna is used as a secondary antenna, the primary antenna may comprise another notch antenna, an external monopole whip antenna or a PIFA. When the primary and secondary antennas are both notch antennas they preferably have orthogonal polarization directions which provides good isolation between them. Essentially this specification discloses a portable wireless terminal having two antennas, at least one of the two antennas being a notch antenna, for use in processing signals operating in accordance with a respective one of two standards. No arrangements are disclosed for use over more than two frequency bands